By late July, you may not see more of cliff swallows than their orange rumps heading south, but for a couple of months they've eddied around North State bridges like summer snowflakes.

But now nesting is done. Roomfuls of flying insects have been caught and turned into feathers and warm heartbeats. Winter remains distant, so young birds and vagrant souls may roam with no sense of urgency.

But the flocks will tend south, to the clime that history tells them is home. For cliff swallows this is deep into South America, a 6,000-mile flight to where they may be seen hawking insects over Argentinian grasslands.

Throughout most of North America, these are the swallows that build their gourd-shaped nests of mud, cemented under eaves, sills and bridges. In Redding, they have long colonized the old Monolith at Turtle Bay. With recent developments, house sparrows have taken over those nests, and the swallows have moved to both the Sundial and Highway 44 bridges.

Architecture like the Sundial Bridge is a boon to cliff swallows. The bridge provides the ceilings and cornices where the birds can construct their nests beyond reach of terrestrial predators. The shoreline provides mud that the swallows can carry, one beak-load at a time, to form their crèches. The river also offers a buffet of insects, which the swirling clouds of swallows catch in flight to feed their young.

Similar conditions made the swallows at the Mission of San Juan Capistrano famous a century ago through a story recorded in the book "Capistrano Nights," by Fr. O’Sullivan.

O’Sullivan saw a shopkeeper shooing away swallows and knocking down their nests in front of his business. When asked where they could go, the shopkeeper said he didn't care; they were pests and he wanted them gone. So the priest invited the swallows to nest at the mission. O’Sullivan saw the swallows building their nests at the mission the next morning. Since then, generations of tourists have visited the mission's annual celebration of The Miracle of the Swallows.